The problem does not specific a G value and supposedly can be solved. Has to do with 1/2 reactions -- Can you take another look. thanks
"The standard free energy change at 25C, ΔGo, is equal to (-38.7) kJ for
2X(CN)63-(aq) + 2I-(aq) → 2X(CN)64-(aq) + I2(s).
Calculate the standard potential for this reaction. Normally, X is Fe. Here it is some unknown metal, allowing for somewhat random values for ΔGo